1. Field of the Invention
This invention relates to a process for conversion of feedstock comprising C.sub.3.sup.+ olefins in the absence of added hydrogen to product comprising non-aromatic hydrocarbons of higher molecular weight than the feedstock olefins and aromatics over a catalyst comprising a crystalline zeolite having large pores and a high silica/alumina mole ratio. The present process results in substantially reduced production of polynuclear aromatics and coke when compared to other olefin conversion processes.
2. Description of Prior Art
It has long been known to contact various hydrocarbon fractions with acidic catalysts generally and, in particular, with solid siliceous acidic catalysts, including those referred to as crystalline aluminosilicate zeolites. Contact of said hydrocarbon feed with said acid catalysts was carried out for a wide variety of reactions including cracking, isomerization, hydrocracking, etc. Representative U.S. patents disclosing and claiming contacting of various hydrocarbon fractions with crystalline aluminosilicates are U.S. Pat. Nos. 3,140,249; 3,140,251; 3,140,253 and 3,140,322.
The contact of paraffinic feedstocks with crystalline aluminosilicate zeolites is also known in the art. The primary reason for contacting paraffinic materials with zeolites has been for the purpose of cracking them, i.e. converting them to lower molecular weight products. Typical applications in this general field would be the use of crystalline aluminosilicate zeolites for carrying out dewaxing reactions, i.e. the cracking of paraffins to low molecular weight materials. U.S. Pat. No. 3,400,072, discloses a dewaxing process with crystalline aluminosilicates generally and U.S. Pat. No. 3,700,585, discloses and claims dewaxing operations carried out with a novel type of crystalline aluminosilicates identified as those of the ZSM-5 type.
U.S. Pat. No. 3,960,978 describes a process for making olefinic gasoline blending stock from C.sub.2 -C.sub.5 olefin mixtures utilizing ZSM-5 type crystalline aluminosilicates. Other U.S. patents relating to converting various paraffins and/or olefins over ZSM-5 type zeolites include U.S. Pat. Nos. 3,760,024; 3,827,968; 4,100,218; 4,120,910 and 4,157,293. U.S. Pat. No. 3,760,024 claims a process for producing aromatic compounds from C.sub.2 -C.sub.4 paraffins, olefins or mixtures thereof. U.S. Pat. No. 3,827,968 claims a process for conversion of C.sub.5.sup.- olefin-containing gas to product comprising aromatics. U.S. Pat. No. 4,100,218 claims conversion of ethane through a series of process steps to a C.sub.5.sup.+ product useful as gasoline, LPG product and light fuel gas. U.S. Pat. No. 4,120,910 claims a process for converting a gaseous paraffinic hydrocarbon feedstock containing ethane to aromatic compounds. U.S. Pat. No. 4,157,293 claims a process for converting C.sub.2 -C.sub.10 hydrocarbons consisting essentially of paraffins, olefins or their mixtures over a catalyst comprising a zeolite having a SiO.sub. 2 /Al.sub.2 O.sub.3 mole ratio of at least 12, a Constraint Index of 1 to 12 and containing zinc and another named metal.
The instant invention is not concerned with hydrocarbon compound conversion in general nor with cracking, isomerization or hydrocracking specifically. It is, rather, concerned with converting C.sub.3.sup.+ olefins to higher molecular weight non-aromatic hydrocarbons and aromatic hydrocarbons which provide exceptional use as gasoline components. The instant invention, further, is not concerned with use of small or intermediate pore size zeolite catalysts, e.g. shape selective catalysts, but rather with use of large pore, i.e. greater than 6 Angstrom, zeolites. It is not concerned with use of catalysts comprising SiO.sub.2 /Al.sub.2 O.sub.3 mole ratios normally used in olefin conversions or with acidic catalysts, but rather with use of high SiO.sub.2 /Al.sub.2 O.sub.3 mole ratio zeolites in catalyst compositions having rather low acid activity.